SAN FRANCISCO — In its first analysis of Martian soil, NASA’s Curiosity rover detected perchlorate salts and simple organic compounds but the probe’s science team can not yet determine if the carbon in these materials is indigenous to Mars.
“When we look in the soil we see a bunch of chemicals in there,” said geologist John Grotzinger of Caltech, project scientist for the mission, during a NASA press conference here at the American Geophysical Union conference on Dec 3.
The rover’s instruments found water, sulfur, and chlorine-containing compounds, including chlorinated methane gas — a molecule that contains carbon. Curiosity detected these chemicals by scooping a small sample of Martian dust and heating it up slowly in a small-internal oven and then analyzing the resulting gases that get released. This was one of the first tests of the rover’s Sample Analysis at Mars (SAM) instrument, a microwave-sized machine that allows scientists to conduct experiments on Mars similar to ones they could if they had a sample of Mars soil in a laboratory on Earth. In addition to looking at gases, SAM used a laser spectrometer to determine the isotopes of different atoms in the sample, which could help understand the complicated history of water and other elements on Mars. Curiosity’s science team thinks that heating the soil sample caused the perchlorates to release chlorine, which readily bonds to other gases such as carbon dioxide, and could have produced the chlorinated methane. We know from previous missions such as Viking and the Phoenix lander that Martian soil contains perchlorate salts, harsh compounds that tend to destroy any organic molecules when heated. Mars’ atmosphere contains carbon dioxide but the team also said that the carbon may simply have been carried from Earth in small amounts since they weren’t able to scrub out every last trace of contamination beforehand.
Determining which of these scenarios is more likely will be the next step. Even if the carbon came from Mars, there will still be a long road to figuring out how it came to be in the soil. The most likely explanation is that it rained to the surface on meteorites and comets, which commonly contain many complex organic compounds. Even if the carbon molecules were created on Mars, it will take time to determine if they are traces of past life.
“Curiosity’s middle name is patience,” said Grotzinger. “And we all have to have a healthy dose of that.”
Prospects are that later results will provide more interesting results about life — the rover is roving around an ancient Martian riverbed, after all — and the scientists are quite pleased with their analysis. They now have good data on the chemistry of Martian dust presently found all over the planet. The fact that it contained no definitive organic compounds was not particularly surprising.
“This is very exposed material,” said Paul Mahaffy, the principal investigator on the SAM instrument during the conference. “There are many processes that could destroy even the organic material that falls in from space: cosmic radiation, hydrogen peroxide, or ultra-high-dose radiation.” The team hopes to later use their analysis as a baseline to compare with other samples, taken from protected places deep underground or in billion-year-old rocks.
Referring to the rumors and excitement that preceded this announcement, Grotzinger said that he had been enthusiastic to see the rover’s instrument was working and beaming back great data. “We’re doing science at the speed of science,” he said, adding that a single experiment is unlikely to produce a “hallelujah moment” now or in the future.
Curiosity Rover Finds Simple Organics, But Long Path Remains to Determine Life
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Curiosity Rover Finds Simple Organics, But Long Path Remains to Determine Life
